1. Field of the Invention
A method and apparatus for molding and packaging bitumen and similar materials.
2. Prior Art
It now is customary to furnish packaged industrial bitumen in paper bags which are ripped off before the bitumen is melted. The paper must be waterproofed for outside storage. Such bags are relatively expensive and are susceptible to tearing. The bitumen usually is poured molten into the bags so that there is a tendency for it to stick and for paper scrap to become mixed into the bitumen when it subsequently is employed, as for roofing and road surfacing. The presence of paper can clog machines used to apply molten bitumen. It also has been proposed to line paper bags with a metal foil or a film of non-melting plastic. Such lined bags are inconvenient and expensive to use. Furthermore, it has been suggested to feed molten bitumen into a flexible plastic bag in which it was hardened. The bags had to have softening point of at least about 50.degree. C above the temperature of molten bitumen and the bags had to be supported and cooled during and after their filling in order to maintain their integrity; moreover the bitumen entered and hardened in the seams and crevices of bags, making their removal difficult.
The equipment previously used included bag filling machines wherein the bags constituted molds for the liquid bitumen. Although this seemed to be quite economical, entailing as it did forming the bitumen in place in its desired configuration and then allowing it to solidify in its packaging container, this arrangement was subject to the aforementioned defects of: difficulty in the choice of bagging materials, difficulty in keeping thermoplastic bags cool enough during and after pouring to prevent the bags from being destroyed, and difficulty in stripping bags from solidified bitumen.